This is a simple test PHP source directory that shows basic functions and coding using PHP.
If you have PHP installed (as I did in macOS) you can run the following:
php -S 127.0.0.1:8000
This runs a simple php server within the current directory.
This should automatically point to index.php when you visit localhost:8000 or 127.0.0.1:8000 which is the same as localhost.
If you do not have PHP installed on your machine, install it and find a similar command to run a quick test server and checkout the barebones application.